U.S. patent application number 17/236983 was filed with the patent office on 2021-10-21 for methods and systems for fabricating nanofiber materials.
The applicant listed for this patent is FERMI RESEARCH ALLIANCE, LLC. Invention is credited to Sujit Bidhar.
Application Number | 20210324540 17/236983 |
Document ID | / |
Family ID | 1000005610847 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210324540 |
Kind Code |
A1 |
Bidhar; Sujit |
October 21, 2021 |
METHODS AND SYSTEMS FOR FABRICATING NANOFIBER MATERIALS
Abstract
Systems and methods for creating coating a substrate with
nanofiber comprise a dual polarity high voltage power supply, a
first wire for wire electrospinning held at positive potential by
the power supply, a second wire held at negative potential by the
power supply and a spooling system for drawing a substrate between
the first wire and the second wire. A slider and a solution chamber
in fluidic connection with the slider are used to slide along the
first wire delivering solution to the wire.
Inventors: |
Bidhar; Sujit; (Carol
Stream, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FERMI RESEARCH ALLIANCE, LLC |
BATAVIA |
IL |
US |
|
|
Family ID: |
1000005610847 |
Appl. No.: |
17/236983 |
Filed: |
April 21, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63013362 |
Apr 21, 2020 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D10B 2321/042 20130101;
A41D 13/11 20130101; A41D 2500/30 20130101; D01D 5/003
20130101 |
International
Class: |
D01D 5/00 20060101
D01D005/00 |
Goverment Interests
STATEMENT OF GOVERNMENT RIGHTS
[0002] The invention described in this patent application was made
with Government support under the Fermi Research Alliance, LLC,
Contract Number DE-AC02-07CH11359 awarded by the U.S. Department of
Energy. The Government has certain rights in the invention.
Claims
1. An electrospinning system comprising: a dual polarity high
voltage power supply; a first wire for wire electrospinning held at
positive potential by the power supply; a second wire held at
negative potential by the power supply; and a spooling system for
drawing a substrate between the first wire and the second wire.
2. The electrospinning system of claim 1 wherein the power supply
comprises a dual polarity power supply.
3. The electrospinning system of claim 1 wherein the spooling
system further comprises: an uncoated substrate spool configured to
hold a spool of the substrate.
4. The electrospinning system of claim 3 wherein the substrate
comprises: non-woven melt-blow polypropylene.
5. The electrospinning system of claim 1 wherein the spooling
system further comprises: at least two free spinning spools
configured to draw the substrate between the first wire and the
second wire.
6. The electrospinning system of claim 1 wherein the spooling
system further comprises: a motor; and a driving spool connected to
the motor wherein the driving spool pulls the substrate into a
roll.
7. The electrospinning system of claim 1 further comprising: a
slider; and a solution chamber in fluidic connection with the
slider, wherein the slider slides along the first wire delivering a
solution to the wire.
8. The electrospinning system of claim 7 wherein the solution
comprises: a co-polymer grade Polyvinylidene fluoride or
polyvinylidene difluoride; N,N-dimethylformamide; and Acetone,
mixed with a Trifluoroacetic acid.
9. A method comprising: holding a first wire at positive potential;
holding a second wire held at negative potential; and drawing an
uncoated substrate between the first wire and the second wire,
wherein a solution on the first wire is coated onto the
substrate.
10. The method of claim 9 wherein: the first wire is held at
positive potential with a dual polarity power supply; and the
second wire is held at negative potential with the dual polarity
power supply.
11. The method of claim 9 further comprising: spooling the uncoated
substrate on an uncoated substrate spool.
12. The method of claim 11 wherein the substrate comprises:
non-woven melt-blow polypropylene.
13. The method of claim 9 further comprising: drawing the substrate
between at least two free spinning spools configured such that the
substrate passes between the first wire and the second wire.
14. The method of claim 9 further comprising: pulling the substrate
into a roll with a driving spool connected to a motor.
15. The method of claim 9 further comprising: sliding a slider
connected to a solution chamber along the first wire; and
delivering solution from the solution chamber along the first
wire.
16. The method of claim 15 wherein the solution comprises a
co-polymer grade Polyvinylidene fluoride or polyvinylidene
difluoride; N,N-dimethylformamide; and Acetone, mixed with a
Trifluoroacetic acid.
17. A method for fabricating a material comprising: coating a
substrate with a nanofiber material; sandwiching the coated
substrate between an outer layer and an inner layer.
18. The method of claim 17 wherein coating a substrate with a
nanofiber material further comprises: holding a first wire at
positive potential; holding a second wire held at negative
potential; and drawing the substrate between the first wire and the
second wire, wherein a solution on the first wire is coated onto
the substrate.
19. The method of claim 17 wherein the outer layer comprises:
melt-blown non-woven spunbound polypropylene filter cloth with an
average fiber diameter of up to 10 microns and open porosity of up
to 10 microns.
20. The method of claim 17 wherein the inner layer comprises:
non-woven spunbound polypropylene filter cloth with a diameter
between 20 microns and 50 microns.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATION
[0001] This patent application claims the priority and benefit,
under 35 U.S.C. .sctn. 119(e), of U.S. Provisional Patent
Application Ser. No. 63/013,362, filed Apr. 21, 2020, and titled
"METHODS AND SYSTEMS FOR FABRICATING NANOFIBER MATERIALS". U.S.
Provisional Application Ser. No. 63/013,362 is incorporated herein
by reference in its entirety.
TECHNICAL FIELD
[0003] Embodiments are generally related to electrospinning.
Embodiments are further related to methods and systems for
manufacturing nanofiber. Embodiments are further related to methods
and systems for coating substrates to create protective materials.
Embodiments are additionally related to methods and systems for
producing a variety of ceramic nanofibers using very low power
output and low voltage DC input using DC to DC voltage converters
with dual polarity and a high voltage DC supply. Embodiments are
further related to methods and systems for fabricating
multi-layered masks.
BACKGROUND
[0004] Electrospinning is a method used to produce polymeric
nanofiber. Electrospinning methods typically require application of
high voltage to a drop of liquid, causing the liquid to become
charged. The charged liquid droplet is then stretched toward a
collector. The elongated droplet dries as it travels to the
collector. The drying fiber is subject to a whipping process that
increases the path of travel, resulting in the formation of very
thin fibers.
[0005] Conventional electrospinning requires sophisticated and
expensive power supply units which are bulky, operate at high input
voltage, and have high power output (e.g. running into the hundreds
of watts). Such systems pose electrical hazards. In cases where it
is desirable to have both positive and negative high voltage
output, two such power supplies are required, effectively doubling
the problems associated with the system complexity, bulkiness, and
safety.
[0006] Conventional N95 masks used by health practitioners, have
only 95% filtering efficiency for particles of 2.5 microns, and
less than 60% filtering efficiency for 1 micron sized particle. As
such, these masks don't offer sufficient protection against
transmission of bacteria and viruses. Conventional face masks are
made from a non-woven polypropylene material using a melt blown
process, resulting in average fiber diameter of 5-10 microns, with
an average pore opening size of about 10 microns. For filtering
smaller particles, the conventional approach is the use of multiple
layers of these filter cloths resulting in a thick face mask that
makes it difficult to breathe. Typical pressure drop across an N95
mask is around 345 Pa at 85 L/min flow rate.
[0007] Accordingly, there is a need in the art for improved
methods, systems, and apparatuses for mass producing filtering
cloth as disclosed herein.
SUMMARY
[0008] The following summary is provided to facilitate an
understanding of some of the innovative features unique to the
embodiments disclosed and is not intended to be a full description.
A full appreciation of the various aspects of the embodiments can
be gained by taking the entire specification, claims, drawings, and
abstract as a whole.
[0009] It is, therefore, one aspect of the disclosed embodiments to
provide a method and system for electrospinning.
[0010] It is another aspect of the disclosed embodiments to provide
a method and system for producing a variety of nanofibers.
[0011] It is another aspect of the disclosed embodiments to provide
methods, systems, and apparatuses for producing a variety of
nanofibers using very low power output and low voltage DC input
using DC to DC voltage converters with dual polarity and a high
voltage DC supply.
[0012] It is another aspect of the disclosed embodiments to provide
methods, systems and apparatuses for producing filtering materials
that can be used in personal protective equipment such as face
masks at large scale.
[0013] The aforementioned aspects and other objectives and
advantages can now be achieved as described herein. Various
additional embodiments and descriptions are provided herein. For
example, in an embodiment, an electrospinning system comprises a
dual polarity high voltage power supply, a first wire for wire
electrospinning held at positive potential by the power supply, a
second wire held at negative potential by the power supply, and a
spooling system for drawing an uncoated substrate between the first
wire and the second wire. In an embodiment, the power supply
comprises a dual polarity power supply. In an embodiment, of the
electrospinning system the spooling system further comprises an
uncoated substrate spool configured to hold a spool of the
substrate. In an embodiment, the substrate comprises non-woven
melt-blow polypropylene. In certain embodiments, the spooling
system further comprises at least two free spinning spools
configured to draw the substrate between the first wire and the
second wire. The spooling system can further comprise a motor and a
driving spool connected to the motor wherein the driving spool
pulls the substrate into a roll. In an embodiment, the
electrospinning system further comprises a slider and a solution
chamber in fluidic connection with the slider, wherein the slider
slides along the first wire delivering a solution to the wire. The
solution can comprise a co-polymer grade Polyvinylidene fluoride or
polyvinylidene difluoride; N,N-dimethylformamide; and Acetone,
mixed with a Trifluoroacetic acid.
[0014] In another embodiment a method comprises holding a first
wire at positive potential, holding a second wire held at negative
potential, and drawing an uncoated substrate between the first wire
and the second wire, wherein a solution on the first wire is coated
onto the substrate. In an embodiment, the first wire is held at
positive potential with a dual polarity power supply and the second
wire is held at negative potential with the dual polarity power
supply. In an embodiment, the method further comprises spooling the
uncoated substrate on an uncoated substrate spool. the substrate
can comprise non-woven melt-blow polypropylene. In an embodiment
the method comprises drawing the substrate between at least two
free spinning spools configured such that the substrate passes
between the first wire and the second wire. In an embodiment the
method comprises pulling the substrate into a roll with a driving
spool connected to a motor. In an embodiment the method comprises
sliding a slider connected to a solution chamber along the first
wire and delivering solution from the solution chamber along the
first wire. In an embodiment, the solution comprises a co-polymer
grade Polyvinylidene fluoride or polyvinylidene difluoride;
N,N-dimethylformamide; and Acetone, mixed with a Trifluoroacetic
acid.
[0015] In another embodiment, a method for fabricating a material
comprises coating a substrate with a nanofiber material, and
sandwiching the coated substrate between an outer layer and an
inner layer. Coating a substrate with a nanofiber material further
comprises holding a first wire at positive potential, holding a
second wire held at negative potential, and drawing the substrate
between the first wire and the second wire, wherein a solution on
the first wire is coated onto the substrate. In an embodiment, the
outer layer comprises melt-blown non-woven spunbound polypropylene
filter cloth with an average fiber diameter of up to 10 microns and
open porosity of up to 10 microns. In an embodiment, the inner
layer comprises non-woven spunbound polypropylene filter cloth with
a diameter between 20 microns and 50 microns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying figures, in which like reference numerals
refer to identical or functionally-similar elements throughout the
separate views and which are incorporated in and form a part of the
specification, further illustrate the embodiments and, together
with the detailed description, serve to explain the embodiments
disclosed herein.
[0017] FIG. 1 depicts a block diagram of an electrospinning system,
in accordance with the disclosed embodiments;
[0018] FIG. 2A depicts a photograph of a nanofiber mat that can be
produced according to the methods and systems disclosed herein;
[0019] FIG. 2B depicts a nanofiber material, in accordance with the
disclosed embodiments;
[0020] FIG. 3A depicts a dual power supply, in accordance with the
disclosed embodiments;
[0021] FIG. 3B depicts a dual power supply, in accordance with the
disclosed embodiments;
[0022] FIG. 4 depicts steps in a method for creating an electrospun
fiber mat, in accordance with the disclosed embodiments;
[0023] FIG. 5 depicts a layered material, in accordance with the
disclosed embodiments;
[0024] FIG. 6A depicts a face mask incorporating a layered
material, in accordance with the disclosed embodiments;
[0025] FIG. 6B depicts an alternative face mask incorporating a
layered material, in accordance with the disclosed embodiments;
[0026] FIG. 6C depicts a face mask structure incorporating a
layered material, in accordance with the disclosed embodiments;
[0027] FIG. 7A depicts an alternative face mask incorporating a
layered material, in accordance with the disclosed embodiments;
[0028] FIG. 7B depicts an alternative face mask incorporating a
layered material, in accordance with the disclosed embodiments;
[0029] FIG. 7C depicts an alternative face mask incorporating a
layered material, in accordance with the disclosed embodiments;
[0030] FIG. 8A depicts a system for coating a substrate, in
accordance with the disclosed embodiments;
[0031] FIG. 8B depicts a slider mechanism associated with an
electrospinning setup, in accordance with the disclosed
embodiments;
[0032] FIG. 8C depicts a spooling system associated with a system
for coating a substrate, in accordance with the disclosed
embodiments;
[0033] FIG. 9A depicts a front view of a spooling system, in
accordance with the disclosed embodiments;
[0034] FIG. 9B depicts a side view of a spooling system, in
accordance with the disclosed embodiments;
[0035] FIG. 9C depicts a top view of a spooling system, in
accordance with the disclosed embodiments; and
[0036] FIG. 10 depicts a flow chart of steps associated with a
method for creating a filtering material, in accordance with the
disclosed embodiments.
DETAILED DESCRIPTION
[0037] The particular values and configurations discussed in the
following non-limiting examples can be varied, and are cited merely
to illustrate one or more embodiments and are not intended to limit
the scope thereof.
[0038] Example embodiments will now be described more fully
hereinafter, with reference to the accompanying drawings, in which
illustrative embodiments are shown. The embodiments disclosed
herein can be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
embodiments to those skilled in the art. Like numbers refer to like
elements throughout.
[0039] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As
used herein, the singular forms "a", "an", and "the" are intended
to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising," when used in this specification,
specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0040] Throughout the specification and claims, terms may have
nuanced meanings suggested or implied in context beyond an
explicitly stated meaning. Likewise, the phrase "in one embodiment"
as used herein does not necessarily refer to the same embodiment
and the phrase "in another embodiment" as used herein does not
necessarily refer to a different embodiment. It is intended, for
example, that claimed subject matter include combinations of
example embodiments in whole or in part.
[0041] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art. It will be further
understood that terms, such as those defined in commonly used
dictionaries, should be interpreted as having a meaning that is
consistent with their meaning in the context of the relevant art
and will not be interpreted in an idealized or overly formal sense
unless expressly so defined herein.
[0042] It is contemplated that any embodiment discussed in this
specification can be implemented with respect to any method, kit,
reagent, or composition of the invention, and vice versa.
Furthermore, compositions of the invention can be used to achieve
methods of the invention.
[0043] It will be understood that particular embodiments described
herein are shown by way of illustration and not as limitations of
the invention. The principal features of this invention can be
employed in various embodiments without departing from the scope of
the invention. Those skilled in the art will recognize, or be able
to ascertain using no more than routine experimentation, numerous
equivalents to the specific procedures described herein. Such
equivalents are considered to be within the scope of this invention
and are covered by the claims.
[0044] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims and/or the specification
may mean "one," but it is also consistent with the meaning of "one
or more," "at least one," and "one or more than one." The use of
the term "or" in the claims is used to mean "and/or" unless
explicitly indicated to refer to alternatives only or the
alternatives are mutually exclusive, although the disclosure
supports a definition that refers to only alternatives and
"and/or." Throughout this application, the term "about" is used to
indicate that a value includes the inherent variation of error for
the device, the method being employed to determine the value, or
the variation that exists among the study subjects.
[0045] As used in this specification and claim(s), the words
"comprising" (and any form of comprising, such as "comprise" and
"comprises"), "having" (and any form of having, such as "have" and
"has"), "including" (and any form of including, such as "includes"
and "include") or "containing" (and any form of containing, such as
"contains" and "contain") are inclusive or open-ended and do not
exclude additional, unrecited elements or method steps.
[0046] The term "or combinations thereof" as used herein refers to
all permutations and combinations of the listed items preceding the
term. For example, "A, B, C, or combinations thereof" is intended
to include at least one of: A, B, C, AB, AC, BC, or ABC, and if
order is important in a particular context, also BA, CA, CB, CBA,
BCA, ACB, BAC, or CAB. Continuing with this example, expressly
included are combinations that contain repeats of one or more item
or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so
forth. The skilled artisan will understand that typically there is
no limit on the number of items or terms in any combination, unless
otherwise apparent from the context.
[0047] All of the compositions and/or methods disclosed and claimed
herein can be made and executed without undue experimentation in
light of the present disclosure. Dimensions or ranges illustrated
in the figures are exemplary, and other dimensions can be used in
other embodiments. While the compositions and methods of this
invention have been described in terms of preferred embodiments, it
will be apparent to those of skill in the art that variations may
be applied to the compositions and/or methods and in the steps or
in the sequence of steps of the method described herein without
departing from the concept, spirit and scope of the invention. All
such similar substitutes and modifications apparent to those
skilled in the art are deemed to be within the spirit, scope and
concept of the invention as defined by the appended claims.
[0048] The embodiments disclosed herein are drawn to methods,
systems, and apparatuses for electrospinning or coating.
Electrospinning can be understood as a process for producing
polymeric fiber. In some embodiments, this can include producing
nanofiber mats. Generally, electrospinning operates by applying a
high voltage to a specially prepared liquid that is formed into
droplets at a dispensing point, such as a needle. The body of the
drop is charged by the high voltage. Electrostatic repulsion
creates a stream of liquid, that is ejected from the dispensing
point, commonly referred to as a "Taylor Cone." The liquid stream
dries as it travels toward a grounded collector. The drying liquid
stream can be elongated by a whipping process. The dried and
whipped fiber collects on the collector in a mat of generally, thin
and uniform fiber, or coats a substrate.
[0049] The embodiments disclosed herein describe compact nanofiber
production systems and coating systems with the ability to produce
a variety of ceramic nanofibers or polymeric materials. The
nanofiber production systems can have very low power output and low
voltage DC input. This is made possible by using a DC to DC voltage
converter with a dual polarity high voltage DC supply, as disclosed
herein.
[0050] FIG. 1 illustrates an exemplary embodiment of an
electrospinning system 100 employing a dual polarity source 115,
for mass production of a nanofiber mat comprising Zirconia, other
such ceramic material (e.g. alumina, Tungsten oxide, Titania,
etc.), or nanofiber filter cloth, polymer filter cloth, etc., using
one or more dispensing needles in a needle array 120.
[0051] The system 100 takes advantage of Corona discharge. Corona
discharge creates oppositely charged ions to neutralize charge
accumulation on the nanofiber mat thereby enabling the creation of
a thick nanofiber mat.
[0052] In FIG. 1, a rotating collector 105 (e.g. a drum collector)
is held at ground potential via ground 170. A Corona discharge
assembly 175 can include a plate 110, having a knife edge 111,
connected to a DC voltage source 115 that drives the Corona
discharge. Nanofibers are ejected from one or more needles in the
needle array 120 as shown. It should be appreciated that in FIG. 1,
four needles in needle array 120 are shown but in other embodiments
the number of needles can vary according to the scale of the system
100 and size of the desired nanofiber mat 125. For example, the
number of needles can be adjusted to accommodate production of a
larger/smaller or wider/narrower nanofiber mat. Arrangement of the
needles in needle array 120 need not be linear. For example, in
other embodiments, the needles in needle array 120 can be staggered
or otherwise configured in any number of ways along needle manifold
155.
[0053] The system 100 can include a dual polarity power supply 115
connected to a solution dispensing assembly 130. The solution
dispensing system 130 includes an actuator 140 that is connected to
a syringe pump 145. The actuator 140 is fixed to a plunger 150 that
is connected to a needle manifold 155. The syringe pump 145
controls the actuator 140, which pushes liquid 160 to the needle
array 120 through the needle manifold 155.
[0054] The liquid 160 can comprise positively charged ions of a
desired material. In certain embodiments the liquid 160 can include
possible precursor solutions including Alumina.fwdarw.Aluminum
2,4-pentadionate+Aceton, Zirconia.fwdarw.Zirconium Carbonate+Acetic
Acid, WO.sub.3.fwdarw.Ammonium meta-tungstate+D.I. Water, and
TiO.sub.2.fwdarw.Titanium Isopropoxide. These solutions can be
added with polymeric solution containing approximately 5-8 wt % of
polyvinylpyrrolidone in Acetone or Ethanol.
[0055] The needle manifold 155 can be configured to include one or
more needle ports 121 that connect the one or more needles in the
needle array 120 to the needle manifold 155. In certain
embodiments, the needle array 120, illustrated in FIG. 1, can
comprise blunt needles with an internal diameter on the order of a
few hundred microns.
[0056] In the embodiment illustrated in FIG. 1, the needle manifold
155 can comprise a manifold and has been designed to hold the
needle array 120 at high +Ve potential. The needle manifold 155 can
be 3-D printed, or can be manufactured according to other known
techniques. The knife edge 111 on plate 110 is similarly maintained
at a high -Ve potential to generate -Ve ions. In combination, this
assembly increases the production rate of the electrospinning
system 100.
[0057] A certain distance, for example, 1-5 centimeters can be
maintained between the needles 120 to avoid squeezing the nanofiber
cone volume that emanates from the needles 120 during use.
Nanofiber constituted liquid emerging from each needle in the
needle array 120 travels to the ground plate 110 in a spiral action
which results in a cone like formation. Since each of the
nanofibers emanating from the needle array 120 are of the same
charge, they increasingly repel each other according to their
relative proximity, thereby squeezing the cone of travel.
Eventually this squeezing action can become sufficiently prevalent
that it will lead to non-uniform deposition of nanofibers on the
drum collector. Thus, in the embodiments disclosed herein, an
exemplary distance between needles in the needle array 120 should
be maintained to prevent this effect. In certain embodiments this
distance can be at least 1 inch. This distance is sufficient to
avoid squeezing of the spinning area from individual needles, due
to charge repulsion, while allowing for some overlap to produce
uniformity in the axial direction of the rotating collector
105.
[0058] Appropriate distance and voltage can also be maintained
between the rotating collector 105 and the knife edge 111 to
prevent the breakdown of air which could result in a spark instead
of ionization. Although the rotating collector 105 and knife edge
111 are illustrated in FIG. 1, in other embodiments, a set of
micro-tipped (e.g., approximately 10 micron tip diameter)
tungsten/metallic needles can also be used to produce corona
discharge, as further detailed in the embodiments presented
herein.
[0059] Thus, in the embodiment illustrated in FIG. 1, the power
supply 115 provides a positive DC voltage to the needle array 120
and a negative DC voltage to the knife edge 111 positioned near the
rotating drum collector 105, which is kept at ground potential. The
potential difference between the needle array 120 and the
drum/knife edge 111 provides the attractive force that results in
the thin liquid jet depositing material 125 on the rotating drum
105. The drum 105 is rotated with a motor 165 connected to a drive
shaft 180, so that a mat of surrounding fiber 125 is deposited on
the drum 105. It should be appreciated that this summarizes the
general functionality of embodiments disclosed herein. Other
arrangements are further detailed herein.
[0060] A photograph of a nanofiber sheet 205 being peeled off a
cylinder is illustrated in FIG. 2A. The photograph in FIG. 2B
illustrates a nanofiber microstructure 210. It should be
appreciated that in other embodiments, other materials can be used
to produce mats of materials and/or to coat underlying substrates
with such materials.
[0061] FIGS. 3A and 3B illustrate an exemplary embodiment of the
dual power supply 115. Two power units (one +40 kV and one -20 kV)
can be assembled inside a housing 305 as illustrated in FIG. 3A. It
should be understood that housing 305 can comprise a metal box, or
other such housing. Each power unit has an individual potentiometer
to vary input voltage, which, in turn, can be used to vary the high
voltage output from approximately 0-40 kV DC. A potentiometer 320
can be provided for the first power supply and a second
potentiometer 321 can be provided for the other power supply in the
housing 305. The housing 305 can further include a display 325. The
housing can provide a voltage sensor port 310 and current sensor
port 315 associated with one power supply, and a second voltage
sensor port 311 and current sensor port 316 associated with the
other power supply.
[0062] FIG. 3B shows inside the assembled power supply 115. The
power supply 115 includes two high voltage converters (one positive
high voltage converter 330 and one negative high voltage converter
331) connected with a connector junction 335. The positive high
voltage power converter 330 is connected to a high voltage DC
output 355. The negative high voltage power converter 331 is
connected to a high voltage DC output 356 The positive voltage
converter 330 has a junction box 340 for connecting to the
potentiometer, voltage and optional voltage/current display.
Likewise, the negative voltage converter 331 has a junction box 341
for connecting to the potentiometer, voltage and the optional
voltage/current display. The output voltage/current sensing ports
can be connected to the digital display unit 325 for easy
readability.
[0063] As illustrated in FIG. 3B, the voltage supply assemblies are
simple and connections can be made easily, without the need for
complicated printed circuit boards, although in certain embodiments
PCBs can alternatively be used. The grounding wire 345 can be
connected to the box 305 for safety purposes. Likewise, spark
protection lug 350 and spark protection lug 351 can be provided. It
is important to select an appropriate length for the spark
protection lugs 350 and 351, and to maintain safe distances between
the high voltage cable and exposed wire to the nearby ground/metal
surface.
[0064] It should be appreciated that the dual polarity power supply
assembly 115 illustrated in FIGS. 3A and 3B is useful for producing
a nanofiber mat. The embodiments disclosed herein can use the dual
polarity high voltage assembly 115 such that one polarity drives
the nanofiber production while the opposite polarity is used for
the negatively charged ions, which results in the Corona discharge
through the specially arranged needle array. Dual polarity also
results in an effective potential drop of up to 60 KV DC. Such high
potential is necessary for mass producing nanofiber coatings on
substrates as described herein.
[0065] In the embodiments disclosed herein, a critical aspect is
the power supply 115, which can use a low voltage DC input and
inexpensive DC to DC voltage converters with a dual polarity high
voltage DC supply. A major advantage realized by this arrangement
is that the power supply 115 can be, for example, limited to 4
watts of output power while maintaining a 0 to 40 kV DC and 0 to
-20 kV DC output in dual polarity mode, simultaneously from a
9V/12V DC battery or a 12 V DC adapter. Thus, the power supply 115
can be characterized as having a nominal input voltage of 12 V DC,
a voltage range of approximately 9 V-32 V DC, an output voltage of
approximately 0 to +40 kV DC and 0 to -20 kV DC, indefinite output
short-circuit protection, and ripple of 0.02.
[0066] FIG. 4 illustrates a method 400 for producing a nanofiber
mat in accordance with the disclosed embodiments. The method starts
at step 405.
[0067] At step 410, an electrospinning system, in accordance with
any of the embodiments disclosed herein, can be configured. The
electrospinning system can take advantage of a dual polarity source
as disclosed in the various systems detailed herein. A solution can
be created for the desired mat fiber material, as illustrated at
step 415. Possible precursor solutions include 7-15 wt % of
co-polymer grade PVDF (Polyvinylidene fluoride or polyvinylidene
difluoride), in 50:50.about.20:80 wt % DMF (N,N-dimethylformamide)
and Aceton. 1-5 wt % of TFA (Trifluoroacetic acid) can be added to
the above solution.
[0068] Once the solution is ready, at step 420 a high positive
potential can be supplied to the solution dispensing arrangement.
As disclosed herein, in some embodiments, the solution dispensing
arrangement can be one or more needles or wires. The rotating drum
can be held at ground potential as illustrated at 425. In other
embodiments, the solution dispensing arrangement can comprise a
rotating spindle with associated solid needles or spikes that are
dipped into a pool of solution. A high negative potential can be
supplied to a knife edge, needle, or wire arrangement to facilitate
discharge as shown at 430, resulting in a thicker fiber mat or coat
of material on a passing substrate.
[0069] The liquid solution is drawn away from the solution
dispenser by the potential difference as illustrated at 435. As the
liquid passes through the air, it is pulled into a fiber that is
collected on the rotating drum, resulting in a fiber mat or coating
as shown at step 440. The process continues until the fiber mat is
of a desired thickness as shown at step 445, at which point the
method ends at 450.
[0070] An aspect of the disclosure provided herein is directed to
methods and systems to increase the filter efficiency of virus
filtering material and masks to close to 100% while keeping the
flow resistance for respiration to a minimum (<5 0 Pa @ 85
L.min) by coating a thin layer of 1-D continuous nanofiber on a low
filter efficiency substrate filter cloth of melt-blown non-woven
polypropylene material.
[0071] FIG. 5 illustrates one embodiment of a filtering material
500 in accordance with the disclosed embodiments. FIG. 5
illustrates a roll 505 of filtering material 500. Exploded view 510
illustrates Nanofiber coated filter cloth 515, that can be
sandwiched between two layers of spun bond polypropylene filter
cloth; inner layer 520 and outer layer 525.
[0072] The nanofiber layer 515 can have randomly oriented 1-D
continuous nanofiber with an average diameter of up to 0.1 micron
and pore opening size of between 0.1-0.3 microns and coating
thickness of between 5.about.10 microns. The thin layer of
nanofiber and open pore size of less than half that of many viruses
(including the COVID-19 virus) ensures such viruses and other
biological or environmental contaminants will be filtered
completely as illustrated by arrow 530. Since only a thin membrane
of a few microns thick nanofiber layer is used, there is also less
pressure drop across this layer. As such, airflow 535 is improved,
which can increase breathability.
[0073] In certain embodiments, the nanofiber layer 515 can be a
thin (up to 0.15 mm thick) 10 gsm melt-blown non-woven
polypropylene filter cloth with average fiber diameter of up to
approximately 10 microns and open porosity of up to 10 microns. The
substrate has an optimum fiber diameter and pore size to act as a
support layer for the nanofiber membrane, thereby providing low
resistance to airflow (e.g. 10 Pa pressure drop at 85 L/min).
[0074] The inner layer 520 can comprise a spun bond non-woven
polypropylene filter cloth (e.g. up to approximately 10 gsm, with a
diameter between approximately 20 micron fiber diameter and
approximately 50 microns). This layer can be in direct contact with
a human's skin and act as a support to the nanofiber coated 10 gsm
melt-blown layer.
[0075] The outer layer 525 can comprise a spun bond non-woven
polypropylene filter cloth, (e.g. approximately 20 gsm, with a
fiber diameter between approximately 20 microns and 50 microns).
This layer also offers far less resistance to air flow due to its
large pore size. The layer also gives added mechanical strength to
the sandwiched filter roll, which is necessary to sustain pulling
force during the face mask manufacturing process and while wearing
the face mask. The combined pressure-drop across these layers is
less than 100.about.130 Pa at an 85 L/min flow rate, which exceeds
the performance of currently available N95 face masks.
[0076] FIG. 6A illustrates a face mask 600 configured from the
above disclosed materials in accordance with the disclosed
embodiments. The face mask comprises a larger mask body 605. A
portion of the mask body 605 around the nose and mouth comprises
the nanofiber sandwiched laminated three-layered filter material
500 disclosed herein (for example in FIG. 5).
[0077] Other features of the mask 600 are intended to create a seal
between the mask 600 and face to ensure contaminated air does not
enter the mask 600. These features can include nose tape 610 formed
along the top edge of the mask body 605 where the mask contacts the
nose bridge. The mask 600 can include vertical stitching 615 along
the center of the mask 600. The mask 600 also includes a border
contour seal 620 such that when the ear strap(s) 625 are put around
the head, there is no gap between the skin and the face mask
600.
[0078] FIG. 6B illustrates another embodiment of a mask in
accordance with the disclosed embodiments. It should be appreciated
that some or all aspects of FIG. 6A can be incorporated in FIG. 6B.
In the case of the mask 650 in FIG. 6B, the mask 650 can be formed
of a cotton material that can be washed. The cotton structure can
include a pocket 655 formed therein generally located around, or
proximate to, the area of the mask 650 covering a user's nose and
mouth. The pocket 655 can be formed of a large pore cotton
material, lace, or other such configuration. Using large pore
material will offer less resistance to air flow in front of
nostrils. Hence there will be less suction of air around the border
of the cotton mask.
[0079] A wire 660 such as a 6 gauge wire can be used on the top
border of the mask 650, so that the shape of the mask 650 can be
contoured to a user's face. An insert 665 can then be inserted into
the pocket 655 in the mask.
[0080] The insert 665 can comprise a Nanofiber coated 10 gsm
melt-blown non-woven polypropylene fabric filter (such as filter
material 500). The Nanofiber coated filter pad insert 665 can have
a 0.1 micron-0.3 micron average pore size. The nanofiber coating
can be between 5-15 microns. Thus, it creates less resistance to
air flow as compared to a standard N95 mask, while also providing
better filtering efficiency (e.g. up to 99% Bacteria filter).
Additionally, the mask 650 of FIG. 6B including the cotton body of
the mask in FIG. 6B can be washed while the nanofiber coated insert
665 pad can be replaced (for example after 1-2 weeks).
[0081] FIG. 6C illustrates another embodiment of a mask template
675 in accordance with the disclosed embodiments. As illustrated in
FIG. 6C, a mask template 675 can be used to properly size the
layers of the filtering material, such as filtering material 500.
The materials can then be fitted to a frame 680 as illustrated in
FIG. 6C. The frame 680 can comprise a foam, plastic, or malleable
wire frame, such that the contours of the frame create a nearly
airtight seal with the user's face.
[0082] For example, in certain embodiments, a mask according to
FIG. 6C, can be fabricated by stamping out the illustrated shape
685 from rubber sheet or silicone sheet or injection molded part.
Next, two layers of cotton fabric with larger pores can be stitched
around the border, with a pocket in between if desired. Then a
single piece of nanofiber coated 10 gsm meltblown non-woven
polypropylene fabric 690 can be connected to the fabric, or
inserted in the pocket.
[0083] The embodiment in FIG. 6C is advantageous because the
silicone/rubber frame 680 will ensure a complete air seal. The
nanofiber coated fabric 690 will ensure 99% filtering efficiency
against COVID19 or other viruses, and the pressure drop of <60
Pa is significantly lower than other filtering masks making the
design more breathable and comfortable to wear.
[0084] Additional embodiments, of personal protective equipment
masks according to the embodiments disclosed herein are provided in
FIGS. 7A-7C. FIG. 7A illustrates a vented mask configuration 700.
As illustrated in FIG. 7A, the vented mask configuration 700
includes a mask body 705 configured with an outer wire 710
configured to conform to a user's face, and ear loop(s) 715. Vented
mask 700 is further configured with vents 720. The vents 720 can be
fitted with filters 725.
[0085] The filters 725 (illustrated in the exploded view) can be
sized to be inserted into the vents 720. The filters 725 can
comprise a nanofiber coated 10 gsm melt-blown non-woven
polypropylene fabric filter (such as filter material 500). The
filter 725 collects unwanted contaminates while allowing airflow at
a lower pressure drop than conventional filtering material.
[0086] FIG. 7B illustrates another embodiment of a silicone vented
mask 730. The silicone vented mask 730 can comprise a mask body 735
which is generally configured with an outward facing surface 740
connected to face flaps 745. The mask body thus forms an inner
orifice into which a user can insert their nose and mouth. The face
flaps 745 create a nearly perfect airtight seal with the user's
face.
[0087] The outward facing surface includes a filter pad 750. The
filter pad 750 can be sized to fit in an opening in the outward
facing surface. The filter pad 750 can comprise a nanofiber coated
10 gsm melt-blown non-woven polypropylene fabric filter (such as
filter material 500). The filter collects unwanted contaminates
while allowing airflow at a lower pressure drop than conventional
filtering material.
[0088] FIG. 7C illustrates a separated view of another embodiment
of a cage style mask 755. The cage style mask 755 can include a
silicone face flap 760 affixed to a mask cage 765. Exhaust valves
770 can be configured on the mask cage 765. Next a filter pad 775
can be configured over the mask cage 765 and exhaust valves 770.
The filter pad 775 can be held in place by a detachable cover 780.
The detachable cover allows the filter pad 775 to be removed and
replaced quickly.
[0089] The filter pad 775 can be sized to fit in an opening in the
outward facing surface. The filter pad 775 can comprise a nanofiber
coated 10 gsm melt-blown non-woven polypropylene fabric filter
(such as filter material 500). The filter collects unwanted
contaminates while allowing airflow at a lower pressure drop than
conventional filtering material.
[0090] In further embodiments, a system 800 to mass produce
nanofiber layers of polypropylene using a low-cost electrospinning
set up are disclosed. The system 800 is illustrated in FIG. 8. The
system 800 can make use of a low-power output, high voltage DC
power supply 115 (as illustrated in FIGS. 3A and 3B), which is
extremely safe and can be operated with a basic power source, such
as mains power, or a 12V battery.
[0091] The power supply 115 can be connected to a free surface wire
electrospinning setup 805 as illustrated in FIG. 8 to produce a
variety of polymer nanofibers in continuous production mode with
diameters ranging from 0.1-0.3 microns.
[0092] The free surface wire electrospinning setup 805 comprises a
wire 810 extended between two stands 815. The wire 810 is held at a
high positive DC voltage by the power supply 115. A slider 820 is
configured below the wire 810, with a polymer solution chamber 825
connected to the slider 820. The slider 820 slides along the wire
810 delivering polymer solution (e.g. PVDF in 10 wt %
DMAC+Aceton+TFA) from the polymer solution chamber 825.
[0093] A spooling system 845 for the non-woven melt blown
polypropylene is arranged above the wire 810. The spooling system
845 can include an uncoated substrate spool 860, where spooled
non-woven melt-blow polypropylene is held, a series of free
spinning spools 865 can be used to direct the polypropylene mat
840.
[0094] A second wire 830, held at high negative DC voltage
potential, can be configured above the first wire 810, with the
polypropylene mat 840 bisecting the path between the first wire 810
and second wire 830. The spooling system 845 runs the polypropylene
mat 840 which serves as the substrate for coating. The potential
difference between the first wire 810 and second wire 830 creates a
nanofiber film 850 from the lower first wire 810 onto the
polypropylene mat 840 above. The slider 820 slides to ensure the
width of the polypropylene mat 840 is fully coated. In this way the
nanofiber 850 is coated onto the polypropylene mat 840. The coated
mat is then spooled into a roll 855 for further processing.
[0095] FIG. 8B illustrates a more detailed view of the
electrospinning setup 805 as disclosed herein. As illustrated in
FIG. 8B, the high voltage steel wire 810 is strung between two
nylon posts 815. A sliding nylon block 820 can be connected to an
aluminum frame 870. The aluminum frame 870 holds the slider 820,
which is driven by a motor 875. A limit switch 880 can be provided.
The slider 820 slides along the aluminum frame 870 delivering
solution to the wire 810.
[0096] In certain embodiments, the high voltage wire 810, which can
have a diameter of 0.2 mm-2 mm, passes through a 0.6 mm-2.5 mm
diameter opening 890 on a plastic tube 895 carrying solution. The
slider 820 holding the solution tank 825 and tube assembly, slides
back and forth on the high voltage wire 810 at a set speed using a
stepper motor control drive unit. The limit switches 880 at each
end of the slider serve to reverse the motor direction when the
slider hits them, resulting in back and forth motion. The speed of
the slider is controlled by a potentiometer and programming
associated with a circuit controller such as an Arduino.RTM. or
other such device.
[0097] As illustrated in FIG. 8B, two additional motors 885, can be
provided--one at the bottom left and one at the bottom right side
of aluminum 2020 frame with a lead screw attached to the frame. The
motors 885 adjust the height of slider assembly vertically in order
to maintain an appropriate gap between the high voltage wire 810
and the substrate filter material passing over it. The slider motor
875 slides the solution tank 825 across the +Ve high voltage wire
810. Its rotation is reversed each time the slider hits the limit
switches 880 located at the end of aluminum frame 870 enabling the
back and forth motion.
[0098] FIG. 8C illustrates an alternative spooling system 851 in
accordance with the disclosed embodiments. It should be appreciated
that some or all of the aspects illustrated in FIG. 8C can be used
in other embodiments disclosed herein. In such embodiments, a 10
gsm melt blown polypropylene filter roll 852, or other such
material roll, can be configured on standoffs 858. Additional
standoffs can be connected to idler spool 853 and idler spool 854
which can be situated at a substantially even elevation. Standoffs
858 can further be used to hold an upper spool over which the
filter material can travel after being coated. The spooling system
851 can be driven by a motor 856 attached to driving spool 857,
where the nanofiber coated filter cloth is wound.
[0099] FIGS. 9A, 9B, and 9C illustrate aspects of a tabletop
nanofiber coating system 900 in accordance with the disclosed.
Aspects of the tabletop nanofiber coating system can be
incorporated in other embodiments disclosed herein. FIG. 9A
illustrates a front view of the system 900, FIG. 9B illustrates a
side view of the system 900, and FIG. 9C illustrates a top view of
the system 900. The system 900 can include a set of hanging
rollers, and idle rollers, which act as support for moving filter
cloth.
[0100] As illustrated in FIGS. 9A-9C a driving spool 905, can be
operably connected to a motor 920. The motor 920 is mounted to a
frame 925. The driving spool 905 serves to wind the coated filter
substrate along idler rollers 930, onto a loading spool 910 which
severs as the structure onto which the substrate filter, which will
be coated, is loaded. An idler roller 915 can be positioned before
the driving spool 905. The idler roller 915 can be maintained at a
preselected temperature with a heating element 940 for evaporating
the solvent residue and to improve adhesion between the nanofiber
layer and substrate layer.
[0101] FIG. 10 details steps associate with a method 1000 for
producing personal protective equipment such as a face mask, in
accordance with the disclosed embodiments. The method begins at
1005.
[0102] Initially, as illustrated at 1010, the electrospinning
system can be configured. The desired solution for coating the
substrate can be selected as illustrated at step 1015. In an
exemplary embodiment, the solution can comprise 10 wt % of
co-polymer grade PVDF (Polyvinylidene fluoride or polyvinylidene
difluoride), in 50:50 wt % DMF (N,N-dimethylformamide) and Aceton.
3 wt % of TFA (Trifluoroacetic acid) can be added to the exemplary
solution.
[0103] At step 1020, with the system fully set up, a positive
potential can be applied to the solution dispensing system and a
negative potential can be applied to the wire above the textile
cloth, as shown at step 1025, so that there is a potential
difference between the wires. The slider associated with the
solution delivery system can slide back and forth as illustrated at
step 1030.
[0104] As such, the dispensing system, such as those illustrated in
FIGS. 8 and 9, creates a stream of nanofiber material that can coat
the substrate passing above, as illustrated at 1035. In certain
embodiments, the stream can comprise a two dimensional plane of
material (using the slider). The liquid solution coats the
substrate as shown at step 1040. At step 1045, the coated material
is then spooled into a roll.
[0105] Next, at step 1050, the spooled roll of material can be
sandwiched between an inner and outer layer as illustrated, for
example, in FIG. 5. The layered material can then be incorporated
into any piece of personal protective equipment including, but not
limited to, a face mask, to prevent the inhalation of environmental
contaminants as illustrated at step 1055. The method ends at
1060.
[0106] In operation, the system can coat nanofiber layers of
desired specifications on a filter substrate with a production
capacity of up to 1000 square meters per day, which is equivalent
to 20,000 face masks. This nanofiber coated filter cloth can then
be cut into the required size (e.g. face masks), ear straps can be
attached, and the masks can be packaged.
[0107] In certain embodiments, the disclosed face masks,
manufactured as disclosed herein, can filter submicron particles
like COVID-19 with close to 99.9% efficiency, offer higher
breathability than existing N95 filter masks and, unlike N95, are
resistant to oil and water. The disclosed coating machine itself
can be built at a low price, almost 20 times cheaper than other
commercially-available nanocoaters. It is also much safer to use
due to the associated power supply. It can be operated with a 12V
battery, at a remote location, where industrial power supplies may
not be readily available.
[0108] Based on the foregoing, it can be appreciated that a number
of embodiments, preferred and alternative, are disclosed
herein.
[0109] In an embodiment, an electrospinning system comprises a dual
polarity high voltage power supply, a first wire for wire
electrospinning held at positive potential by the power supply, a
second wire held at negative potential by the power supply, and a
spooling system for drawing a substrate between the first wire and
the second wire. In an embodiment, the power supply comprises a
dual polarity power supply.
[0110] In an embodiment, of the electrospinning system the spooling
system further comprises an uncoated substrate spool configured to
hold a spool of the substrate. In an embodiment, the substrate
comprises non-woven melt-blow polypropylene.
[0111] In certain embodiments, the spooling system further
comprises at least two free spinning spools configured to draw the
substrate between the first wire and the second wire. The spooling
system can further comprise a motor and a driving spool connected
to the motor wherein the driving spool pulls the substrate into a
roll.
[0112] In an embodiment, the electrospinning system further
comprises a slider and a solution chamber in fluidic connection
with the slider, wherein the slider slides along the first wire
delivering a solution to the wire. The solution can comprise a
co-polymer grade Polyvinylidene fluoride or polyvinylidene
difluoride; N,N-dimethylformamide; and Acetone, mixed with a
Trifluoroacetic acid.
[0113] In another embodiment a method comprises holding a first
wire at positive potential, holding a second wire held at negative
potential, and drawing a substrate between the first wire and the
second wire, wherein a solution on the first wire is coated onto
the substrate. In an embodiment, the first wire is held at positive
potential with a dual polarity power supply and the second wire is
held at negative potential with the dual polarity power supply.
[0114] In an embodiment, the method further comprises spooling the
uncoated substrate on an uncoated substrate spool. the substrate
can comprise non-woven melt-blow polypropylene.
[0115] In an embodiment the method comprises drawing the substrate
between at least two free spinning spools configured such that the
substrate passes between the first wire and the second wire. In an
embodiment the method comprises pulling the substrate into a roll
with a driving spool connected to a motor.
[0116] In an embodiment the method comprises sliding a slider
connected to a solution chamber along the first wire and delivering
solution from the solution chamber along the first wire. In an
embodiment, the solution comprises a co-polymer grade
Polyvinylidene fluoride or polyvinylidene difluoride;
N,N-dimethylformamide; and Acetone, mixed with a Trifluoroacetic
acid.
[0117] In another embodiment, a method for fabricating a material
comprises coating a substrate with a nanofiber material, and
sandwiching the coated substrate between an outer layer and an
inner layer. Coating a substrate with a nanofiber material further
comprises holding a first wire at positive potential, holding a
second wire held at negative potential, and drawing the substrate
between the first wire and the second wire, wherein a solution on
the first wire is coated onto the substrate. In an embodiment, the
outer layer comprises melt-blown non-woven spunbound polypropylene
filter cloth with an average fiber diameter of up to 10 microns and
open porosity of up to 10 microns. In an embodiment, the inner
layer comprises non-woven spunbound polypropylene filter cloth with
a diameter between 20 microns and 50 microns.
[0118] It will be appreciated that variations of the
above-disclosed and other features and functions, or alternatives
thereof, may be desirably combined into many other different
systems or applications. Also, various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims.
* * * * *